At present, free cloud storage services are provided for file uploading and downloading. However, capacities of cloud storage devices provided by different manufacturers are limited. When a user have registered cloud storage services from various cloud storage providers, he must know which cloud storage device files are uploaded and worries if the capacity of one of the cloud storage devices is full. Thus, it is convenient for users to manage the files on the cloud storage devices and the capacities of the cloud storage devices. In addition, complicated user authentication is required when a file transferring is raised.
On the other hand, user accounts and passwords are required for different cloud storage platforms when a file transferring between the cloud storage platforms is performed. Security issue is consequentially raised if one of cloud storage platforms stores the user accounts and passwords of the other cloud storage platforms. Therefore, it is an important object to develop a method for file transferring without storing the user accounts and passwords of the cloud storage platforms.